This document contains supplemental release notes for Multimedia Services V3.3 for DIGITAL UNIX (MMS).
This document contains critical release notes from previous releases. If you are upgrading from a version of MMS prior to V2.0, you may not have access to these important notes for intermediate versions of MMS. Please read these supplemental notes thoroughly before attempting to install or use MMS V3.3.
Specifically, files recorded with earlier versions of MMS would appear much darker when played back on other systems and files recorded on other systems would appear lighter or washed out when played back on pre-V2.0 MMS systems.
Because this problem has been corrected in V2.0, JPEG files can now be exchanged correctly with other systems, but corrective measures may need to be taken for files recorded with earlier versions of MMS.
There are several alternatives for playing back old data.
You may set the environment variable in a script which you use to start an application. This would turn on the old JPEG data format support for the older application while still allowing new applications to make use of the new JPEG data formats. For instance, you might start an application called communique with the following script:
setenv MME_JPEG_OLDQ 1
setenv COMM_HOME /usr/local/isvapplets/Communique
setenv LM_LICENSE_FILE $COMM_HOME/license.dat
$COMM_HOME/communique
Because old files are incorrectly encoded and won't have the intended visual appearance on systems which conform to the JPEG standard, DIGITAL recommends reencoding data by either using jpegconvert(1) or recapturing/recompressing from the original source.
The table below shows the mapping between the old settings and new settings for both the hardware (AV300 & AV321) and software (SJPG) compressors. The quality settings exposed by the API range from 0 to 10,000, but user applications typically convert this to a percentage. Percentages are used in the table below.
| Supplied
Setting | Effective pre-2.0
H/W Quality | Effective pre-2.0
S/W Quality | Effective V2.0
Quality 0% | 0% | 61% | 0%
| 10% | 0% | 65% | 10%
| 20% | 0% | 69% | 20%
| 30% | 0% | 73% | 30%
| 40% | 0% | 76% | 40%
| 50% | 0% | 80% | 50%
| 60% | 0% | 84% | 60%
| 70% | 0% | 88% | 70%
| 75% | 4% | 90% | 74%
| 80% | 22% | 92% | 80%
| 90% | 59% | 96% | 90%
| 100% | 96% | 100% | 100%
| |
|---|
As you can see from the table, the hardware compressors previously reached their maximum compression setting (and lowest quality) at a quality setting of approximately 74% rendering the remaining 3/4 of the scale useless. On the other hand, it was only possible to access the top 40% of the quality range when using the software compressor. In V2.0, this has all been normalized to allow access to the full range of compression values for all compressors, with matching quality scales.
The video and ICM services use a quality setting of 0-10000. Internally to MMS this quality setting is mapped to something called the 'Q factor' which is a value used to scale the suggested visually weighted quantization tables K.1 and K.2 in Appendix K of ISO 10918-1. Higher values of Q provide higher levels of quantization (larger quantization steps) and more compression, so the range of Q is inversely related to the range of quality settings. The acceptable range for Q is from 255 to 0, corresponding to quality settings of 0 to 10,000.
Previously, in the Sound & Motion J300 (AV300) and FullVideo Supreme JPEG (AV321) drivers, the quality factor was incorrectly mapped to a Q factor in the range of 950-10. Because the Q factor has a maximum value of 255, the quality settings were severely compressed and clipped as can be seen from the table above.
The SJPG software JPEG CODEC by contrast was mapping the quality setting to a Q factor range of 100-0. This resulted in less than half the full quantization scale being available.
Starting with V2.0, the quality settings of 0-10,000 are correctly mapped to Q factors of 255-0 for all JPEG compressors.